Hi there @Jaguwar can you try disabling Hardware Acceleration in settings to see if this resolves the issue?
You’ll find this in Settings --> Additional Settings --> System --> Hardware Acceleration
If that does not work, try loading those websites on incognito mode to see if they load. If the sites load properly, it may be an issue with an extension.
If you have HTTPS Everywhere try disabling it as there’s currently an issue with such extension, please check this post I can not enter Google account - #11 by bagsymallone