8 months after the first, three star rating:
the add-on has been improved, is now much more stable and works well. Protects the privacy and saves loads of time. There are still sites where the settings need to be updated manually, but not too many and I'm not letting perfect be the enemy of good.
The "old" review: Good idea, but unstable implementation. Some pages hang (e.g. connect.garmin.com, with trust arc), with no way of cancelling the process, the only way is to disable the CoM. There seems to be an option to not run the CoM on a page (a check box "keep running on this site?") but it does not affect the process in any way.
Please fix it and/or provide some way of giving you feedback and learning about fixes.

Absolutely fantastic! Thank you for developing this extension!

Doesn't work on most sites.

Ne fonctionne pas sur la plupart des sites que je visite, clubic ou frandroid notamment.

A must for every avid Internet user. Works like a charm on most sites, and improves the experience on the internet extremely, especially when looking for news articles on sites I don't regularly visit. It would be interesting, if there are further lists that could be included, or whether new lists are included in the Standard .json.

O add-on que precisaba!! Marca todas as opcións dos avisos de cookies da GDPR seguindo unhas sinxelas liñas configurábeis. Tamén podes marcar que non funcione en certas páxinas. Aforrando tempo sen parar!! Grazas!! :)

Just doesn't work, ever.

Disabling doesn't work so I can't test the websites I'm working on in Firefox. Also, the log just stays empty even after months of use and it behaves weirdly on stackoverflow. (It pops up and flashes every single time I visit the site as if it was handling a consent popup, but there is no consent popup to handle on every single visit. And I have already consented to them before even installing consentomatic.) Otherwise nice work.

Excellent module from a liable source, unfortunately, I had to uninstall it since it was blocking the access to my online bank. Otherwise, it works perfectly on a lot of websites.

very funny and scarry to see in the PiP opting out frame, scrolling through 100's of data thieves.

Tested against over 30 websites, didn't do anything.. I had to answer all consent popups manually.. Most of them were Finnish news sites. If developer wants to test, https://www.ampparit.com is good place to start, it collect news links from tens of different Finnish news sites. Consent-O-Matic fails on all of them.

It's a lovely extension. I am working a project and this has helped me a lot.

Even if it's not working on all sites, I still enjoy it. Hope it stays supported in the future. Great work and thank you for saved nerves and time. ✌

Works

Très pratique mais malheureusement trop zélé : il m'empêche d'accéder à mon espace perso sur le site de ma banque, même lorsque je le désactive pour ce site. Dommage.