IDN - Internationalized Domain Names - are domains with characters from some different characters set than the default Latin. Regtons Registry in default don’t provide domain validation by IDN table, but there is a possibility to install tables and set for domain name validations.
IDN tables - Samples from other registries in IANA registry can be download here: https://www.iana.org/domains/idn-tables
Create file with content bellow and save as "cz.txt" to /tables directory inside Regtons Registry
U+002D # HYPEN-MINUS
U+0030 # DIGIT ZERO
U+0031 # DIGIT ONE
U+0032 # DIGIT TWO
U+0033 # DIGIT THREE
U+0034 # DIGIT FOUR
U+0035 # DIGIT FIVE
U+0036 # DIGIT SIX
U+0037 # DIGIT SEVEN
U+0038 # DIGIT EIGHT
U+0039 # DIGIT NINE
U+0061 # LATIN SMALL LETTER A
U+0062 # LATIN SMALL LETTER B
U+0063 # LATIN SMALL LETTER C
U+0064 # LATIN SMALL LETTER D
U+0065 # LATIN SMALL LETTER E
U+0066 # LATIN SMALL LETTER F
U+0067 # LATIN SMALL LETTER G
U+0068 # LATIN SMALL LETTER H
U+0069 # LATIN SMALL LETTER I
U+006A # LATIN SMALL LETTER J
U+006B # LATIN SMALL LETTER K
U+006C # LATIN SMALL LETTER L
U+006D # LATIN SMALL LETTER M
U+006E # LATIN SMALL LETTER N
U+006F # LATIN SMALL LETTER O
U+0070 # LATIN SMALL LETTER P
U+0071 # LATIN SMALL LETTER Q
U+0072 # LATIN SMALL LETTER R
U+0073 # LATIN SMALL LETTER S
U+0074 # LATIN SMALL LETTER T
U+0075 # LATIN SMALL LETTER U
U+0076 # LATIN SMALL LETTER V
U+0077 # LATIN SMALL LETTER W
U+0078 # LATIN SMALL LETTER X
U+0079 # LATIN SMALL LETTER Y
U+007A # LATIN SMALL LETTER Z
U+00E1 # LATIN SMALL LETTER A WITH ACUTE
U+00E4 # LATIN SMALL LETTER A WITH DIAERESIS
U+00E9 # LATIN SMALL LETTER E WITH ACUTE
U+00ED # LATIN SMALL LETTER I WITH ACUTE
U+00F3 # LATIN SMALL LETTER O WITH ACUTE
U+00F6 # LATIN SMALL LETTER O WITH DIAERESIS
U+00FA # LATIN SMALL LETTER U WITH ACUTE
U+00FC # LATIN SMALL LETTER U WITH DIAERESIS
U+00FD # LATIN SMALL LETTER Y WITH ACUTE
U+010D # LATIN SMALL LETTER C WITH CARON
U+010F # LATIN SMALL LETTER D WITH CARON
U+011B # LATIN SMALL LETTER E WITH CARON
U+0148 # LATIN SMALL LETTER N WITH CARON
U+0159 # LATIN SMALL LETTER R WITH CARON
U+0161 # LATIN SMALL LETTER S WITH CARON
U+0165 # LATIN SMALL LETTER T WITH CARON
U+016F # LATIN SMALL LETTER U WITH RING ABOVE
U+017E # LATIN SMALL LETTER Z WITH CARON
Regtons Registry support two methods of character writing. You can use U+00E4 and also u\0034
# ./rreg -c config.yaml
2019/08/24 17:01:52 Listening on secure [::]:700
2019/08/24 17:01:52 Using following IDN tables: arabic cz latin
From this moment, you can go to GUI -> TLD Edit and set up the required IDN table to activate the IDN table list.