The landing speed should be instant considering
ignoring distance statement + time travel feat (even the movement of slash too normally :d).
Saitama's
time travel causes the
divergence of timelines, which they diverge as bubbles, He
interacts and attacks Garou from the bubble which it appears instantly (
also he still hears and perceives everything normally in the timeline which supports the timeline diverges until Saitama chooses a bubble). Also it's God's power as well which might support it.
Even if it wasn't accepted as instant, It should be MFTL+.
The landing speed perception blitz Flashy flash and even Blast. Flashy Flash has a
statement of being able to move at the speed of light + the name of the chapter 198, paralles Sonic and Flash,
which Flashy Flash is referred as the speed of light + even
FTL is
supported by
feats, supports the statements more. the reaction time of speed of light (0.000000003336 second) can be used for how fast DS moves the total distance, which considering it's above the clouds, it should be like 10-20 km? maybe more.
It would be around 10000-20000 times speed of light which is MFTL+.
If Flashy Flash's statement is not accepted, it is still fine as there is
Gamma Ray Burst. Gamma ray burst
moves at 0.999999 speed of light /
nearly at speed of light.
A casual Saitama jumps and
blocks himself against it. which
casual Saitama is a version of Saitama Garou had copied at that moment. Then Garou
fights Blast, Blast moves and reacts to everything. And then
he even reacts and moves faster than Serious Saitama which is massively superior to Casual who reacts and blocks himself against GRB. so Speed of light reaction speed can still be used. So it would still be around 10000-20000 times Sol.
Also there are other situations for Casual Saitama which Garou copied, or a version which Blast's superior to.
A casual Saitama can react to Geryuganshops rock's speed which moves at near light speed stated by Murata. Casual Saitama is superior to Meteoric Boros, which he was even able to throw Saitama almost at the light speed.
If the total distance is accepted as higher (
like edge of the universe or distance of stars etc etc.) this timeframe would still be acceptable and making the speed feat way higher.
I believe MFTL+ is nearly guaranteed and that it will be accepted. Infinite speed might be accepted.