@BoneTone Well your entitled to your opinion of course but i do not share it.
Until the certain flash sites i use shut the door permanently then i shall carry on using flash. I don't think adobe quite realises how much flash content is still out there and that includes commercial as well as public sectors.
It's not my opinion, it's just the state of things. I'm certain Adobe is well aware of how few users will be truly affected by this. I recall about 2 years ago there were only ~17% of users who even saw a piece of Flash, let alone wanted or needed to use it. It's even fewer now.
I was going to bring up the Flashpoint site archiving the legacy Flash around the web that @LonM linked, but I couldn't recall its name. That'll be a good resource for anyone whose favorite games go missing. Articles over the past couple years have been suggesting users download the Flash files so they have them for safe keeping and to be able to run them locally. As well as usual a legacy browser they use solely for the purpose of using Flash.
I'd also like to reiterate my primary point which seems to have been overlooked. Adobe & the browsers aren't doing this to force users to stop using Flash, but to drive developers to use better technologies. Users don't really care -- they just want to access their desired content. Precisely how that content is created & delivered is on the minds of very few users. Come 2021, content delivered through Flash will begin another sharp decline, to become almost extinct. The gaming industry, however, is not going extinct, and legacy games with enough popularity will be ported to new, safer technology. This is a good thing.
Perhaps you have moved on in the last year, but here's a solution for others in the same situation. Yes it is simple, no it does require time. Definitely isn't for a home-user that's happy with the in-browser Settings dialog box. I will describe it broadly, you'd have to lookup the details.
Basically, be aware that there are 3 ways to "admin" Chromium-based browsers. Via GPO centrally, via registry locally, and via JSON locally for a stand-alone install. Your "corporate Chrome" uses one of the first 2, your requirement as a non-admin user can be satisfied by the 3rd option.
Prepare the policies to your liking. Download the Google Chrome MSI and ADMX admin-policy template. Import the policy files on a test PC, play around in the GPedit.msc to set policies, see which settings you want, maybe some settings are deprecated and you need to pick an alternative, maybe you want to force-install a few extensions on first run. When it is all just right, test it on Vivaldi by changing the RegistryPath to HKLM\SOFTWARE\Policies\Vivaldi. I mean, export the Chrome policies, edit REG file, import as Vivaldi policies. This is the step that OP has probably done already on his home PC.
Convert those registry policies to a JSON file. In Vivaldi address bar, type chrome://policy which will promptly redirect to vivaldi://policy. Click the "Export to JSON" button, and save the file, maybe open in Notepad and clean it up if you like.
Place the file to apply policies. Take the prefs-JSON file you created/cleaned in step2 above, rename it to master_preferences without a file-extension. Place it in the same folder as vivaldi.exe. For example, you may have a portable/stand-alone install where the EXE is located at D:\Apps\Vivaldi\Application\vivaldi.exe. The policy file would sit right next to the EXE, at D:\Apps\Vivaldi\Application\master_preferences.
Testing first. I repeat, test all this at home if you can. If not the trust certificate, try applying some other settings/policy in this method. Delete the Vivaldi policies that you imported into HKLM registry in step1, restart, verify that the expected settings are definitely being applied from the JSON file. If something isn't right, you'd rather catch it at home (preferably in a VM) than waste time and pull your hair out at work.
Having said that, I confirm that this method does work with Vivaldi/Opera/ChrEdge/Chromium. Obviously, my pick of the lot is Vivaldi. It's just a shame that the old Opera engine (my beloved!!!) was junked, and then the new Opera went to pot... The only real alternative left is Firefox and THAT is a different can of worms.
Caution: If you are force-installing an extension on Opera/ChrEdge, it has to be from, and exist on that browser's own Extension-Store. No matter whether you are doing so using GPO/reg/json.
If it helps, know that it has taken you longer to read and comprehend all this, than it will take to actually do it. 🙂
For the curious, in the address bar go to about:about in Chrome/Chromium to see a full list of internal settings/diagnostics pages that you can lookup in all Chrome-based browsers (including Vivaldi).