Snaky It need to configure ACME and Let’s Encrypt. It can be done on WebUI, no need to work it on CLI.
First, go to Datacenter and ACME, then click Add to register an account.
Type the account name and email address, then select Let’s Encrypt V2 on ACME Directory. Click Accept TOS.
Go to the node, and then Certificates.
Click Add under ACME.
Select HTTP in Challenge Type, and enter the node FQDN, then click Create.
Select the ACME profile and click “Order Certificates Now”.
After awhile, the certificate will downloaded and appear on Certificate area.
Additional Note
It can be also implement with Cloudflare. It will need to configure a Challenge Plugin under Datacenter. It also need to obtain the CF_Token and CF_Zone_ID from Cloudflare portal. For the DNS API, it will be Cloudflare Managed DNS.
After that, go to the node and do the same to add a ACME, but this time the challenge type will be “DNS” and select cloudflare plugin. Then click create and order certificate now.
Refer
https://pve.proxmox.com/wiki/Certificate_Management
https://computingforgeeks.com/secure-proxmox-ve-with-lets-encrypt-ssl/
https://3os.org/infrastructure/proxmox/lets-encrypt-cloudflare/
