Good sci-fi bl is very rare. Is there anything specific you like about Little Mushroom? Might help us find you something similar.
If it's a good bl sci-fi you want then I'd recommend reading "The invasion day" but it's a novel...if you're ok with it.
I guess the plot (in a way) & art style
That is fine thank you very much
LM has a pretty unique plot. Maybe you'd like No.6? It's a post-apoc(?) world where an escaped experimental subject meets a boy named Shion. The anime is also good if you'd prefer to watch that instead.
https://www.mangago.me/read-manga/no_6/
Another manhwa with gorgeous artstyle (not sci-fi):
https://www.mangago.me/read-manga/heaven_official_s_blessing/
Some sci-fi bl that I like:
https://www.mangago.me/read-manga/host_in_down/
https://www.mangago.me/read-manga/500_nen_no_itonami/
https://www.mangago.me/read-manga/nobody_knows/
Some apocalyptic bl that I like:
https://www.mangago.me/read-manga/uruwashiki_shuen/
https://www.mangago.me/read-manga/undead_tsuyuhisa_fumi/
https://www.mangago.me/read-manga/zon_bl/
Thank you ! I added 2 of them to my list rn : D
Any bl like Little Mushroom?