> stuck on a derivative of Ubuntu 18.04 [...] as our project was being developed in Python, we were stuck on 3.6

I might be missing something but why do you need to rely on the OS provided Python version? Newer versions that 3.6 should run on older Ubuntu versions. You could have installed newer versions using the deadsnake PPA for example onto 18.04 up until earlier this year (since LTS only has a 5 year support window, and deadsnakes only supports active LTS versions).