I've used Flameshot for a while and can say it is definitely the best of many tools I've tried. The direct upload to imgur is particularly nice.
I like postimages.org.
:|
https://i.imgur.com/ZtR60qw.png
I love nesting screenshots into screenshots by simply hitting the PRTSC button muliple times
https://i.imgur.com/9NKvWko.png
https://i.imgur.com/n8Mwh1Z.png
EDIT:
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And you should also install "hoverzoom" under brave broser with multiple blockers:
(It has a blur tool too, but I don't recommend blurring sensitive data as if the area under the blur kernel is 1, the sum of the pixel values will be the same before and after the blur, and if an attacker recognizes which font and size it is from other parts of the screen, they use could dictionary attack for the text with the sum of the pixels as the hash to be cracked.)
Thank you!