I have been using DeepL's Pro Starter subscription (trial period) for the past three weeks. It has been slightly useful in that DeepL would nag me less, and I could use the Android app to translate German texts instead of Google Translate, but the benefits were nullified by the immense annoyance of DeepL continually logging me out of their system. I noticed this both on Firefox (with adblockers and without) and Chromium (with adblockers and without), with and without VPN usage.
I sent them a support ticket, and I got a pro-forma reply that asked me for more detail that I had *already provided in the initial message*. At that point I gave up and decided that I'll end the subscription before the end of the trial period, which ends about a week from now.