That is only required when automating. You can use manual DNS and enter TXT records yourself. You said you were looking for a temp solution while you searched for new hosting company. This might be easiest.
It looks like your hosting service has already moved to something else. Your site is not serving a valid cert:
And, you said they were "dropping support for Lets Encrypt". But, I don't see any record of past Let's Encrypt certs for your domain:
Given this, I think you are better off just getting a new hosting service and don't worry about a temp solution. Let's Encrypt has these suggestions