Adding USA copyright, trademark, registration and publishing superscripts

I hope this inquiry makes sense. I'm having a hard time expressing myself, as I have a very limited knowledge of language expression differences on digital platforms around the world.

We wish to continue adding extensive metadata to the FLAC files to our hopefully archive-quality digital music library for our radio station's airplay and stream resource. The goal is to create digital files with the essential metadata found in the liner notes of well-produced albums in CD format. We also wish to keep the original "lossless" quality of the music made available to us, recognizing that no digital representation is truly lossless. (For our purposes, 44.1/16 bit or better is considered lossless.)

The growing industry trend is to offer only direct downloads rather than physical albums with embedded ISRC codes and with liner notes containing comprehensive credits regarding the release. From our point of view, this is troublesome to those of us that wish to maintain a high-quality resource for airplay. It should also be a concern for anyone that appreciates music and musicians, but that's another topic for a rainy day.

This problem is exacerbated by the fact that no two sources of downloadable recorded material ever seem to agree on any format or content presentation.

As I implied at the beginning, I apologize for my overall ignorance of the terminology associated with fonts, characters, and other word combinations used for the symbols necessary to convey information in a global (world) environment. Suffice it to say that for Vorbis comments, Field Names need to be ASCII English characters while the Field Values need only be UTF-8 compliant regardless of the native language of the reader.

There are certain characters or symbols that we would like to incorporate in our version of the Vorbis comments that we use to embed this metadata. The symbols I would like to use include the normal copyright , sound recording publisher and trademark registration characters, optionally as superscript for the trademark registration symbol. I presume these too need to be UTF-8 compliant.

With an extended USA keyboard and using Windows 10 Character Map with the MS Reference Character Set, it is easy enough to add these two marks: ® using keystrokes Alt+0174 and © using Alt+0169 respectively for tagging popular music using mp3tag. Apparently I could also add the Sound Recording Copyright symbol using U+2117, but I don't know what that means.

I understand that this topic may have been addressed in different ways on this forum, but can anyone help me understand what "I" need to do to ensure that we can add these symbols to Vorbis comments with confidence that they are UTF-8 compliant? Would they appear correctly if they were downloaded by someone in another country with a different operating system and language?

If you are not sure what happens elsewhere in the world, you could still use
(C), (R) and (TM)

For the record:
(no pun intended)

The last one (U+2117) is the ℗ symbol:

IMHO you can not be absolutely sure that the target system shows them correctly. If they don't have the correct font or don't read this values with the same encoding (UTF-8) as you wrote it, the visible characters on the target systems are out of your control.

It’s 2021, all of these symbols are well supported in standard operating systems (Windows, Linux, Android, iOS, macOS). However, some hardware or embedded players (e.g. in cars) might be lacking font support, at least for the circled P. In some cases, this will mean that they fall back to a standard font, which may be a bit ugly, and in other cases they might show a generic replacement character like a box or question mark. However, that’s rather unlikely and should not stop you from using the proper symbol.

In some circumstances, players might misinterpret UTF-8 for UTF-16 or Windows-1252, but that’s s as well a defect that should be fixed by their developers, not by users like yourself.

Lossless only have a meaning in the digital space.

For localization, just ensure that UTF-8 is ticked in the software used. Almost all modern software store text in either UTF-8 or UTF-16, and those encodings works worldwide on all modern OS'es. At least as long as the developer use the frameworks provided. UTF-8 is compatible with "English" ASCII in the sense that if an app expect ASCII and is served UTF-8 it will be OK with the "English" characters (the others will be garbled).

As long as you encode in UTF-8, I wouldn't think too much about how it works around the world. It is the most compatible, but it will never be perfect. As Crissov says, the font file used may be missing the characters even though the software can decode the encoding used. (iOS and Android tend to use fonts where not all characters are available as a way to save memory). It is not much you can do about that, except do what ohrenkino suggests.
In Windows you can get ℗ by holding Alt and on the numeric keypad type + and then type 2117. On Macs you could press "fn" or "Ctrl-Cmd-Space" and then search for "sound recording copyright".