with the new commander card Arixmethes if seen a lot of talk regarding blood moon / blood sun and i understand the intereaction with arixmethes. im simply looking at the interaction for etb abilities with a sun or moon in play. From what i understand they changed it with blood sun so that if a land would lose abilities nothing triggers on entering ie Simic Growth Chamber enters untapped and does not bounce a land, My big hang up is that i think ive seen also that blood moon will interact the same so a land like simic growth chamber enters untapped doesnt bounce and has t: add {R}. So do both replace etb or is it just sun where it specically strips away non mana abilities?
With the rule change from Ixalan, if Blood Moon or Blood Sun is already on the battlefield, abilities of the form "as [this permanent] enters the battlefield" or "... enters the battlefield tapped" on a nonbasic land or a land of any kind, respectively, won't work as that land enters the battlefield (C.R. 614.12, 614.1c-d; C.R. 305.7 and 305.6 apply to Blood Moon) — not just abilities of the form "when [this permanent] enters the battlefield". This is the case for Blood Moon since it would remove those abilities (among other abilities) from that land when it turns it into a Mountain (C.R. 305.7, 305.6).
Would that imply in some sense a Simic Growth chamber actually enters untapped normally and then becomes tapped?
No. Since it wouldn't have "Simic Growth Chamber enters the battlefield tapped" with either Blood Moon or Blood Sun on the battlefield, Simic Growth Chamber will enter untapped by default (C.R. 110.5b). (In any case, assuming Simic Growth Chamber retained that ability [which it doesn't], Simic Growth Chamber would not enter the battlefield untapped then become tapped, but rather would enter the battlefield already tapped — that ability replaces how Simic Growth Chamber enters the battlefield [C.R. 614.12, 614.1d, 614.6].)
EDIT (Jul. 9, 2019): One rule was renumbered with Core Set 2020.
EDIT (Jul. 31, 2021): Clarification.
BWTeysa, Orzhov Scion Combo
GUEzuri, Claw of progress Morph
GUBSidisi, Brood tyrant
RWGisela, Blade of Goldnight Random red white cards i dont use.dec
GBLoam Pox
Modern
UBFaeries
GBWGoyfless Abzan
On Squirrels
On Risen Executioner
BWTeysa, Orzhov Scion Combo
GUEzuri, Claw of progress Morph
GUBSidisi, Brood tyrant
RWGisela, Blade of Goldnight Random red white cards i dont use.dec
GBLoam Pox
Modern
UBFaeries
GBWGoyfless Abzan
On Squirrels
On Risen Executioner
EDIT (Jul. 9, 2019): One rule was renumbered with Core Set 2020.
EDIT (Jul. 31, 2021): Clarification.