[SOLVED] I was using the wrong ICS link for this. I got it to work. Next, I wanna see whether I can merge several calendars into one CalSync item on my rM2.

I also tested a hand-written comment on my rM2 and re-sync my Google Calendar with a little change online (Change spelling of a title) and the change on Google synced, but the handwritten bit remained. Good. Now, the next thing is trying the capability to sync without an actual install of a client that will sync on a regular basis. I also understand that CalSync will sync on a regular basis with Google, however, I still have to see whether it will also update my document online. I use the Cloud option.

Using Linux for a long time (I also teach it at a local college), I would first ask @Stephen Brooks : Which distro/version of Linux do you use ? They have different ways to add menu items. Your way to Pin it on the taskbar is fine. But it will not add it to your actual menu. In a regular setup, there are other details added to the specifications of the menu item creation. There has to be the category (Apps, Games, Programming, etc....) as well as the actual command to run it. Often, the command could also involve parameters pointing to a configuration file. If you use Linux Mint, which is based on Ubuntu/Debian, I could help you manually creating the menu item. Prior to using Mint, I was using Ubuntu, also based on Debian. I do not know the actual BASH script code to create the menu item, but this should be possible.

OK, I just realised you use Linux Mint, just as I do. Yes, right-clicking on the icon and pinning it to the taskbar should work. Also, I would recommend that you do not leave CalSync extracted under the downloads directory. This directory should (I sauy SHOULD) only contain downloaded archives, not running programs. You may leave it there, but if you cleanup the download directory, you could accidentally delete this too. One of the location for installing programs is under /opt. You need to use sudo to create the directory, move the files around and change ownership and access rights. In the menu item creation, you then point to the /opt/CalSync/ directory to run the actual program. Also, under Linux, there is not "update/upgrade" method for CalSync. Basically, you extract the archive somewhere temporary (like /tmp). Then, create a backup directory of the current install location, and copy all the files from the new archive over the existing ones. Eventually, someone will have to create (and TEST!!!) the packages and how they behave under different distros as well as ultimately providing packages for .deb, .rpm, .AppImages, and Flatpaks. Those packaging types each have a specific structure and requirements that will provide a seamless installation, just as under Windows. I never created such packages, I am not the best to create this. But someone in the development team would need to take the existing directory structure, prep the actual structure for the various package types, and script the process.

I will have to re-do the entire process and re-check my steps. As for the timezones, they already match between my Google account and my rM2.