Iam using templ https://templ.guide/ in combination with htmx. I rebuilded various of html components of https://www.patternfly.org/components/all-components/ - but as you mentioned, I also couldnt find good vanilla JS libraries for more complex components - and I dont feel I am capable to build a e.g. battle tested datepicker from scratch.

How others handle this?

P.S. I have seen some people using e.g. flowbite, but I havent tried it out: https://github.com/themesberg/flowbite/issues/812