1. Yes,
kah-shar in 1Sam 18:1 is in the perfect tense and feminine... so what? Are these people and you? saying that because the word is feminine in that text, then it de facto signifies a homosexual 'binding' between Jonathan and David?

2. Consulting some of the most respected and reliable sources re: Hebrew and O.T. as to this word as it appears in 1Sam 18:1; BDB (Brown, Driver, Briggs)
A Hebrew and English Lexicon of the Old Testament and
Englishman's Hebrew and Chaldee Concordance and Keil-Delitzsch
Commentary on the Old Testament vol. 2, NONE even hint of anything untoward in the relationship between Jonathan and David.
BDB-Genesius: "the life of Jonathan was bound up with the life of David"
Keil-Delitzsch: (summary) with ongoing strained relationship between Saul and David who committed himself to remain under the authority of Saul despite the strong animosity of Saul toward David. And thus, Jonathan committed himself to follow David for the remaining days (for life), i.e., Jonathan made a covenant of friendship with David. And, as a pledge of his loyalty to the covenant made, he (Jonathan) gave David his clothes and his armor.
Thus, I maintain that the problem has to do with using the right text, using proper Grammatical-Historical hermeneutic and one's presupposition that respects the LGBTxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx agenda. One or more applies to all who try to suggest that there was a homosexual relationship between David and Jonathan.
If the above is not sufficient to answer your query, then I apologize for not supplying what you are desiring.

It is true that gender does not always refer to sex for inanimate items like boats and airplanes are often being given female names, but we're dealing with human to human relationships here. But, the fact that in the two Hebrew-English Interlinears I quoted, they only use the Hebrew qashar parsed as perfect third feminine singular in three verses, this one about Jonathan and the other two concerning women, Gen 38:28 "midwife"; Josh 2:21 "Rahab". In the majority of the occurences of qashar there is no gender indicated, but these three are feminine, and in over ten other occurrences it is parsed as male. I do not see how this can be ignored or passed over.
When seen in the context where the word for Jonathan's love is the Hebrew 'ahabah in 18:3, it adds to the question of homoerotic content. The word 'ahabah in regard to human love can be traced as follows:
First occurrence - "And Jacob served seven years for Rachel; and they seemed unto him but a few days, for the love/'ahabah he had to her. And Jacob said unto Laban, Give me my wife, for my days are fulfilled, that I may go in unto her."
The word is clearly connected with the sexual there. The next three occurrences of the word concerning human relations are about Jonathan's love for David, 1 Sam. 18:3; 20:17 & 2 Sam. 1:26. The next occurrence is where Amnon committed sex with his sister Tamar because he loved her so much, but later this sexual love 'ahabah is written in this manner:
"Then Amnon hated her exceedingly; so that the hatred wherewith he hated her was greater than the love/'ahabah wherewith he had loved her. And Amnon said unto her, Arise, be gone." (2Sam 13:15, KJV)
The last use of 'ahabah in reference to Jonathan as before mentioned, is the following:
"I am distressed for thee, my brother Jonathan: very pleasant hast thou been unto me: thy love to me was wonderful, passing the love of women." (2Sam 1:26, KJV)
In both words "love" it is 'ahabah and Jonathan's love is compared to "women", NOT wife or wives or mother or mothers. The only translation to vary from the word "women" that I've encountered is the CEV which translates it here as "wife", but the word is plural. How can the love of multiple women, a harem, be a higher love than the singular love of one person to one person? If the word should be translated "wife" or "wives" here, why is it not translated that way? The words were available.
The matter of simple homosexual relationships between males is hotly debated, and I'm more and more seeing the evidence of honest exegesis and a sound hermeneutic is on the side of those contending that the biblical record does not condemn each and every form of male on male homoerotic relationships. The LGBTQ agenda is of course perverted but I'm not writing about that sort of corruption, but about the difficult situation of the regenerate child of God sitting in the pews hearing themselves preached into hell.
I've begun to see the anti-homosexual use of the Scriptures to be shallow proof texting not any different than the technique of the cults who line up proof texts to prove the Son of God is a created being. They superficially appear such until you begin to exegete and examine each text in its own context. This matter would not be such an important issue if it were not for the fact that homosexuals merely for their sexual/love relationships are condemned to hell based on such scant, superficial evidence in the Scriptures.
The complementarian approach of trying to define sin by the creation, which God calls "good", is baseless. We live in a fallen world and not every deviation from the good of creation can be called sin. It is God's law that defines sin, not the standard of goodness in God's creation. I know those convinced against their will remain unconvinced still, but I felt it important to bring this up. I'll close my input on this matter here except to say, I've not found where Bible scholars have not clarified 1 Sam. 18:1-3 as used by the LGBTQ supporters as seen in. The conservative Bible scholars I can find nowhere refuting this. It is just glossed over and not addressed.
"The scripture states that Jonathan’s soul is bound[iv] with David’s. Bound in Hebrew is נִקְשְׁרָ֖ה, meaning, “to bind, conspire,” but is parsed as perfect third feminine singular[v]. This verse details the beginning of an attraction, and is feminine on the part of Jonathan."
https://blog.smu.edu/ot8317/2016/05/09/1-samuel-18-23-the-queerness-of-david-and-jonathan/I'll end my input at this.