For example, if you use the link Https://lemm.ee/feeds/u/Corr.xml?sort=New, all your previous posts will be displayed.
Instead of lemm.ee you need to specify the instance where the user in question is registered. And instead of Corr you have to enter the username. For example https://discuss.tchncs.de/feeds/u/fryboyter.xml?sort=New. That would be in this case my contributions.