Edgerunner brings back the feature of
receiving effects according to the block right below the player's feet instead of the actual block the player is standing on,
which was reported in MC-1133
and fixed in 23w18a.
Basically, in 23w18a and above,
you can't eliminate the effects provided by soul sand, magma blocks, slime blocks,
honey blocks, ice, etc. by standing on the edge of the blocks anymore.
It was indeed a bug which has lasted for over 10 years, but it was also a feature interesting enough that many players don't want it to be fixed nor removed.
So, here it is again.
Edgerunner has implemented the feature as a gamerule, which can be configured easily by in-game commands.
To enable the feature, run:
/gamerule edgerunner true
And to disable it, run:
/gamerule edgerunner false
Edgerunner is licensed under the GNU General Public License v3.