IMO the learning curve for caddy is almost non existent, and just about anything you might want to selfhost almost certainly has a quick simple caddy configuration you can copy paste with just updating the relevant domain. Personally learning curve for caddy was probably way lower than figuring out the edge cases of apache that I was using before

I used to use npm. If you know it and you're happy, use it.

It took me 3 times until I understood and got caddy installed. First, I tried using it via podman and failed. In the end I just installef it via dnf and it worked without any problems. Learning a caddy file is easy. I'll never look back. It's so nice and easy. Easier than npm but no gui but that's not needed

Minor nitpick: NPM stands for nodejs package manager not Nginx proxy manager

Anyway I personally would recommend that you move to Caddy.

Another option would be Nginx/Apache with ACME.sh

I'm a Nginx(SWAG) user. It looks like more and more tutorials are leaning towards Traefik or Caddy with some using NPM. If you rely on those to deploy new services I would consider that.

I can recommend Caddy myself, it is dead simple to configure

If you are using docker have you looked at Traefik to act as your reverse proxy to replace nginx proxy manager?

I use Cloudflare for DNS so would prefer using a DNS challenge. I will change this at some point but not yet ready to!

Since you are already using Cloudflare, and you are moving to an upgraded VPS, why not incorporate Cloudflare's Tunnel/ZeroTrust? The nice thing about their ZeroTrust Tunnel is that you don't have to punch holes in your UFW firewall, no port forwarding or NAT on your external firewall/router. It's just one tunnel that handles your traffic, and Cloudflare takes care of the certs.There is a section that allows you to implement the DNS challenge/verification. You seem experienced so it's fairly easy to deploy. The caveat is that you have to have a proper domain name, and use the issued Cloudflare nameservers. I picked up a domain name at NamesCheap for $1.75 USD.

OP, I came across this, thought it might be worth a look see.

https://dockflare.app/

NPM+ didn't work worth a damn for me. No proxies would forward, I have no clue why and couldn't figure it out. It was like I was turning knobs that weren't connected to anything. But YMMV.