Seeking Official Sources (Or Good Homebrew) For Some PC Races

[Malimar]

Okay, so, I've got this campaign setting I've been running since 3.5e, so it has a number of no-longer-supported features, including some races dating from the days of "you can play any monster" (and also I halved all listed LAs). And it had a global-flood-for-500-years dealie, so most of 3.5's core seafolk races are well-represented, even dominant, while such are assumed by 5e to not be suitable for PCs for various reasons.

I've been able to track down official sources for most of the setting's races -- mostly Mordenkainen Presents: Monsters of the Multiverse, which superseded all previous sources for half the list. But there remain many common-in-the-setting races that have no official support that I can find.

So I seek citations pointing to official support, or to high-quality community-vetted homebrew, for the following as player races:
Kuo-Toa
Locathah
Merfolk (10ft land speed is fine, Combat Wheelchair is in play and canonically frequently used by merfolk)
Mongrelfolk (currently having players just use Custom Lineage from Tasha's Cauldron of Everything, which is honestly probably better for the purpose than previous editions' officially-published mongrelfolk, so I could just keep with that)
Sahuagin
Myconid
Necropolitan
Skum

[Twelvetrees]

Kuo-Toa
I've got nothing, sorry.

Locathah
Official stats are in Locathah Rising, an adventure WOTC created for Extra Life.

Merfolk
Two semi-official sources from WOTC. These are about as trustworthy as most Unearthed Arcana material.
Merfolk in Plane Shift: Zendikar (https://media.wizards.com/2016/downloads/magic/Plane%20Shift%20Zendikar.pdf) - see page 12
Merfolk in Plane Shift: Ixalan (https://media.wizards.com/2018/downloads/magic/plane-shift_ixalan.pdf) - see page 12

There's also some homebrew sources I can point to, but none of them look to have been that highly vetted.
Deepwater Merfolk by GuesssWho (https://forums.giantitp.com/showthread.php?399439-Deepwater-Merfolk-(Race))
Merfolk by DiscipleofBob (https://forums.giantitp.com/showthread.php?491961-Merfolk-Race-PEACH)
Merfolk by VertDeLion (https://forums.giantitp.com/showthread.php?497421-Custom-Races)
Merfolk by Argothair (https://forums.giantitp.com/showthread.php?398386-New-5e-Player-Race-Merfolk)

Mongrelfolk
Nothing official, I'm afraid.

A couple of homebrew options.
Mongrelfolk by eleazzaar (https://forums.giantitp.com/showthread.php?419927-Mongrelfolk-Homebrew-5e-race-(with-subraces)-peach)
Mongrelfolk by JNAProductions (https://forums.giantitp.com/showthread.php?558090-Mongrelfolk)

Sahuagin
One homebrew option I'm familiar with:
Sahuagin by zminseo (https://forums.giantitp.com/showthread.php?574822-Sahuagin-and-Myconid-Race)

Myconid
Two homebrew options:
Myconid by LoneStarNorth (https://forums.giantitp.com/showthread.php?525099-Mushrooms-and-Spiders-Two-Monsters-Adapted-as-Player-Races)
Myconid by zminseo (https://forums.giantitp.com/showthread.php?574822-Sahuagin-and-Myconid-Race)

Necropolitan
I'd take a look at the Reborn or Dhampir in Van Richten's Guide to Ravenloft. Reborn is probably a close substitute.

Skum
I'm not seeing anything for Skum, unfortunately.

[Malimar]

Kuo-Toa
I've got nothing, sorry.

Locathah
Official stats are in Locathah Rising, an adventure WOTC created for Extra Life.

Merfolk
Two semi-official sources from WOTC. These are about as trustworthy as most Unearthed Arcana material.
Merfolk in Plane Shift: Zendikar (https://media.wizards.com/2016/downloads/magic/Plane%20Shift%20Zendikar.pdf) - see page 12
Merfolk in Plane Shift: Ixalan (https://media.wizards.com/2018/downloads/magic/plane-shift_ixalan.pdf) - see page 12

There's also some homebrew sources I can point to, but none of them look to have been that highly vetted.
Deepwater Merfolk by GuesssWho (https://forums.giantitp.com/showthread.php?399439-Deepwater-Merfolk-(Race))
Merfolk by DiscipleofBob (https://forums.giantitp.com/showthread.php?491961-Merfolk-Race-PEACH)
Merfolk by VertDeLion (https://forums.giantitp.com/showthread.php?497421-Custom-Races)
Merfolk by Argothair (https://forums.giantitp.com/showthread.php?398386-New-5e-Player-Race-Merfolk)

Mongrelfolk
Nothing official, I'm afraid.

A couple of homebrew options.
Mongrelfolk by eleazzaar (https://forums.giantitp.com/showthread.php?419927-Mongrelfolk-Homebrew-5e-race-(with-subraces)-peach)
Mongrelfolk by JNAProductions (https://forums.giantitp.com/showthread.php?558090-Mongrelfolk)

Sahuagin
One homebrew option I'm familiar with:
Sahuagin by zminseo (https://forums.giantitp.com/showthread.php?574822-Sahuagin-and-Myconid-Race)

Myconid
Two homebrew options:
Myconid by LoneStarNorth (https://forums.giantitp.com/showthread.php?525099-Mushrooms-and-Spiders-Two-Monsters-Adapted-as-Player-Races)
Myconid by zminseo (https://forums.giantitp.com/showthread.php?574822-Sahuagin-and-Myconid-Race)

Necropolitan
I'd take a look at the Reborn or Dhampir in Van Richten's Guide to Ravenloft. Reborn is probably a close substitute.

Skum
I'm not seeing anything for Skum, unfortunately.

Awesome, infinite thanks! I'll be goin' through these and picking out what I like, to point players to.