As with most software, you could do without Tailscale, it's just easier to use their software which glues a bunch of pieces together, rather than glue it together yourself, unless you have good reason to, which is entirely possible.
Specifically:
> As a result, the application is now available at https://libations, with a valid LetsEncrypt certificate, on all of my machines!
So you'd have to setup a VPN on all of your devices, setup a DNS server, set all you're machines to use that DNS server, setup a reverse proxy, buy a domain, setup Let's Encrypt for it... or just use Tailscale. No one's forcing you to use Tailscale, it's your time and you get to choose to use it however you like, but unless you want to make that you're project, instead of the libations app, why spend time configuring all that you don't have to? (Because you want to is an entirely valid reason, mind you.)
tailscale handles the dns, you just need to install tailscale on all the boxes you want on your tailnet.
EDIT: I'd suggest trying it out, they have a very generous free tier. I didn't really understand how much more seamless and feature rich it was than a standard vpn setup that i've ever set up for my home network.
Specifically:
> As a result, the application is now available at https://libations, with a valid LetsEncrypt certificate, on all of my machines!
So you'd have to setup a VPN on all of your devices, setup a DNS server, set all you're machines to use that DNS server, setup a reverse proxy, buy a domain, setup Let's Encrypt for it... or just use Tailscale. No one's forcing you to use Tailscale, it's your time and you get to choose to use it however you like, but unless you want to make that you're project, instead of the libations app, why spend time configuring all that you don't have to? (Because you want to is an entirely valid reason, mind you.)