[KronisLV]

Personally, I've also had decent experiences with Keystore Explorer: https://keystore-explorer.org/

I actually wrote about using it on my blog, which has plenty of screenshots: https://blog.kronis.dev/tutorials/lets-run-our-own-ca

It's pretty good for having your own simple CA, self signed certificates or anything of the sort, as well as having a nicer interface for anything that's not one of the ACME providers (e.g. Let's Encrypt) or when you don't need CLI or automation.