Is F the boss skill? I've remapped a bunch as a lefty. Mine isn't working either but the only mods we share are Valheim+ and BepinEx. With V+ it might matter which things are active too.

I've also got FarmGrid, Dodge on Double Tap, and Valheim Backups active. Don't remember all the inactive ones off the top of my head, but none of them are on your list.

Edit: It wasn't the mods, unless something unmapped my key. My F skill went back to being F. Lefty problems.