They're probably on MOSWIN
https://osagebeach-mo.gov/ArchiveCenter/ViewFile/Item/2395 (MOSWIN mentioned on Page 6).
www.krmsradio.com
Yep, I'd agree and it does look like they made or are making the move over to Moswin.
Being that Osage Beach is mainly in Camden County, they will probably be given a talkgroup within the talkgroup range that the county is assigned. As it is now, Camden county does not have any talkgroups listed under Moswin so someone needs to use ID Search mode on the sites in that area and see if they can find them and get them submitted to the Moswin database!
Moswin seems to assign the talkgroup ranges to the counties first and then any towns or cities or fire districts within a county will get a talkgroup within the range assigned to the county.
I do know that a small part of Osage Beach is in Miller County, MO so Osage Beach could get talkgroups in the Miller County range which is listed and in the 289xx talkgroup range. Any new unknown talkgroups in the 289xx range could be Osage Beach.
I guess it depends on which of the two counties Osage Beach's tower or sheriff department is located in.
That news link you posted was from 2019 which is not abnormal that it takes that long for an agency to get the equipment and make the move to Moswin.