ISTA+ is bit cumbersome to get hands on at first but once you get the hang of things, "fairly" straightforward. I'll try to round up some steps to get hold of ISTA.
!!! Everything is in there, for DIYer's. !!!
One usually don't need to have the latest app, just the data portion.

Also,
https://www.newtis.info/tisv2/a/en/ <<---- provide feedback to get access to,

eg. OEM sites, pay to play, especially if you want ETK access to latest vehicles (with vin's),
https://bmwtechinfo.bmwgroup.com/

bmw aos
https://aos.bmwgroup.com/
https://aos.bmwna.com/

EDIT's:
disclaimers:
i'm not an expert on these tools, just someone that enjoy using them as a hobbyist (and occasional DIYer)
with that said, there are two folks online that have contributed, and continues to contribute to bmw tools scenes
a) sedoy << original public ista standalone, last public standalone release was 4.37.4x
b) shawnsheridan << all things ista/ispi updates, i do see this user presence in this forum time and time,
now, there is bmw factory service tech present in this forum ----> to them, all these are probably seen as "pirates"
or, is it...anyway... there are tons, and tons of tutorial contents online, including youtube for all of these materials, where to get, how to get (some what legit) licenses, etc.
just going to focus on what i have from my notes
two methods to grab the bits, i have 5Gb up/down fiber isp, so bandwidth isn't much of issue,
a) mega.nz << what i use most, not free, but i pay month to month as needed,
b) torrents << have used, free
Even if you are not hooking up to the car to run diag, get test plans, etc., ISTA still has some benefit of finding repair operations for your vehicle including torque specs, etc.
Kina like your repair/maintenance encyclopedia, from the factory,


The SIB's, however, won't be with ISTA. << you can hunt those down freely, eg. nhtsb site under g01/g02 products, i typically visit this site, once a month,
The latest that is floating around online as a (free) ista standalone installer seems to be 4.39.2x, here,
https://mega.nz/folder/v3pS3LKY#LgNFPfPjcuCm3BsRENZrEw << are we allowed in this forum to post link as such?
Probably simplest to start with standalone variant of ista, albeit bit older than what's currently available (requires some sort of license)
tbd...
EDIT's:
Making available 4.39.2x ISTA "standalone" (license pre-activated, good for life i guess) in google drive, once upload complete (~134 GB) shouldn't need to resort to mega.nz and torrent methods.
4.39.2x --> i-level of g01 s15a is 22-11-540 sw version
And latest psdz 4.43.31 --> i-level of g01 s15a is 23-07-550 sw version
https://drive.google.com/drive/folders/1t_ntFs0RsE93guaAG97dFDBkmlsu2M6U


Close the ista, remove the 4.39.2x psdzdata/ folder and extract the 4.43.31 psdzdata archive in the same path, << there maybe a simpler, turn key solution to doing this all manually,

When ista starts up, the programming data still says 4.39.20, i think there is way to have that reflect the correct data version (???).









