Ubuntu announced its 21.04 (Hirsute Hippo) release almost 9 months
ago, on April 22, 2021, and its support period is now nearing its
end. Ubuntu 21.04 will reach end of life on January 20, 2022.
It’s all good now. I have upgraded to 21.10 and have solved all of my issues now. Thanks for all the advice.@zero-wine, if you don't know what the above means, it means you have a fairly limited amount of time to upgrade to the next version - 21.10, as you're on interim releases. If you don't, the OS will stop getting updates and, after a fairly small period of time, will no longer be able to upgrade at all as the servers are taken down/repurposed. Using an out-of-support release is a horrible idea, especially if it's connected to the 'net.
It’s all good now. I have upgraded to 21.10 and have solved all of my issues now. Thanks for all the advice.