Can’t confirm. Syncs several manitu.de accounts for me continuously on a Fairphone 3.
(Although this reminds me I haven’t installed the latest update yet, I’m still on IMG-e-0.10-p-2020080666687-dev-FP3, but you even had that on a Fairphone 2, so I guess it still counts).
It is possible, see here … Uninstall default apps - #29 by AnotherElk … and the following post after that.