If you value reliability over ANYTHING, then buy Shimano.
YouTubers often receive early units and they serve as beta testers. Bad strategy? These YouTubers had the battery with tabs and not springs, which caused most of the concerns.
Your concern over shilling is also warranted. Anybody who has a discount code on anything has an interest in you spending more, mathematically. And so if you don't see a discount code on l-twoo, they don't stand to benefit, which is worse. If they don't make money from it but then users report problems, then they just shit themselves in the foot twice.
I'm very happy with my 5 er9, but I kind of want them to fail to see what happens. I enjoy the tinkering and the grind of making my own bike infinitely more than buying off the shelf pre packaged branded stuff. Shimano for me is a patent troll and SRAM is the worst assemble of engineers in recent bike history, so I will get out of my way to try alternatives.
I still use a Shimano group on an old bike. That stuff will never die. You probably should buy Shimano if your key concern is reliability. L-twoo electric groups didn't exist a year ago. Nobody can tell you how they age long term. They may age like fine wine, they may age like Lindsay Lohan. Do you want modern day Lindsay Lohan on your bike?
I have to agree with many of these. I am now already >5000km on my first eR9. I have to admit, almost half of which are indoor Zwift rides (don't blame me, I am a fair-weather rider and don't like to be miserable on the bike during winter). I got another set for my wife's bike. These days, with discount codes, you can almost buy two eR9s for a price of Shimano 105 Di2. That is just a no brainer for me when I want to maintain more than two bikes. It's also convenient to have "spare" parts on one bike if/when anything goes wrong on the other. Some stores on AE are now listing individual parts already.
I am actually thinking of getting another set for my commuter bike. Still trying to figure out if I should get eGR or eR9. I want to run 2x on eGR, but not sure if that works. I'd imagine if the firmware allows, it should be straightforward since everything else is identical. I do have an extra front derailleur to use, so that would be great.
I am hoping my eR9s would age like Lindsay Lohan on fine wine diet.