This is a little article i thought id do based off of my own research, common thoughts & UPG's, and the mythology itself as to what altars/deities you typically or never would put next to eachother. I cant really say i have any sources from this aside from tidbits of the various writings and lore ive read over the past few years.
Deity - Altars NOT to be in proximity to
Odin (or wodin if you prefer) - Surt altars / Jotun (etin, giant's) altars (a lot of people count loki as an exception to this) / Hel altars (although she could be classified under etin altars, its fair to point out that most altars or deities would prefer not to be in proximity to Hela's altar witht he exception of a handful)
Thor - Jotun altars, for obvious reasons / A special note to not place a Jormungandgand shrine anywhere near it / Not so much an altar but just a note to avoid putting wetstones or sharpening stones on his altar given he still has a piece lodged in his head according to lore
Heimdall - Loki altars / Jotun altars (starting to see a pattern emerging?)
Tyr - Distance from Loki altars (this one is actually somewhat debated over, a portion of UPG's supposedly say there is a meutual dislike between Loki and Tyr) / Fenrir? (its questionable but i thouht id put it on this list anyways, best not tempt the fates, or, norns i guess)
Iduna - As far as i know there arent any real taboos about iduna being in proximity to other altars, but i think it would be a safe assumption that it might be a good idea to have some fair distance from a Loki shrine
Baldur - (big "well duh" from most people i expect) One usually wouldnt put a Loki altar next to an altar to Baldur
Skadi - Loki altars
Jormundgand - Thor altars / Perhaps aesir altars in general?
Fenrir - Tyr altars / Aesir altars
Surtr - Aesir altars in general, especially Odin altars
Hel - I honestly have no clue as to Her ladyships preferances, if anyone here works with her id be more than thrilled to know if she has any specific "donts" about altar proximity / I do however know from UPG and a decent amount of writings that Loki is a deity that is happy to share an altarspace with his daughter
Loki - Tyr altars (based on UPG's)
If anyone has their own opinions theyd like to contribute, or would like to share theior own UPG's id strongly encourage it. If theres anything here that needs correcting please comment so. I hope you all found this helpful and remember that sometimes its not the same case for everyone. Thanks for reading.