Codes of conduct not encoded in UTF-8 that include non-ASCII characters prevent the server from starting

Codes of conduct including non-English characters such as ü or ß do not work and prevent the server from starting. Since all languages are supported as separate files, it makes no sense that letters from other languages are not supported. The following error is shown in the console:

[21:12:38] [ServerMain/ERROR]: Failed to start the minecraft server
java.lang.IllegalArgumentException: Failed to read Code of Conduct file de_de.txt
        at aro.bU(SourceFile:135) ~[server-1.21.9-rc1.jar:?]
        at aro.<init>(SourceFile:110) ~[server-1.21.9-rc1.jar:?]
        at net.minecraft.server.Main.a(SourceFile:221) ~[server-1.21.9-rc1.jar:?]
        at net.minecraft.server.MinecraftServer.a(SourceFile:304) ~[server-1.21.9-rc1.jar:?]
        at net.minecraft.server.Main.main(SourceFile:220) ~[server-1.21.9-rc1.jar:?]
        at net.minecraft.bundler.Main.lambda$run$0(Main.java:54) ~[?:?]
        at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
Caused by: java.nio.charset.MalformedInputException: Input length = 1
        at java.base/java.nio.charset.CoderResult.throwException(CoderResult.java:279) ~[?:?]
        at java.base/sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:405) ~[?:?]
        at java.base/sun.nio.cs.StreamDecoder.lockedRead(StreamDecoder.java:217) ~[?:?]
        at java.base/sun.nio.cs.StreamDecoder.read(StreamDecoder.java:171) ~[?:?]
        at java.base/java.io.InputStreamReader.read(InputStreamReader.java:188) ~[?:?]
        at java.base/java.io.BufferedReader.fill(BufferedReader.java:160) ~[?:?]
        at java.base/java.io.BufferedReader.implReadLine(BufferedReader.java:370) ~[?:?]
        at java.base/java.io.BufferedReader.readLine(BufferedReader.java:347) ~[?:?]
        at java.base/java.io.BufferedReader.readLine(BufferedReader.java:436) ~[?:?]
        at java.base/java.nio.file.Files.readAllLines(Files.java:3395) ~[?:?]
        at aro.bU(SourceFile:132) ~[server-1.21.9-rc1.jar:?]
        ... 6 more