Caddy is great, been using it for a long time and made the switch from v1 to v2. The biggest negative, IMO, is that examples are usually for NGINX. This is fine if all you have to do is to translate the nginx 5-liner into a Caddy 1-liner, but for nextcloud, the code was a bit more complicated and required some googling (as people had that issue before and their forums are helpful).
LLMs can also be useful for translating nginx directives to caddy.
Weird, who are those people saying that? Never heard of TS, Obsidian, or PFSense being open source.
TS is the only one I use, and I know they employ people working on headscale.