a keyboard layout for xkb to type out runes. (made for personal use so if you'd like to extend this then please fork and credit the original)

runic

default partial alphanumeric_keys
xkb_symbols "basic" {

    include "us(basic)"
    include "level3(ralt_switch)"

    // Layer Shifting (Taking A (AC01) as an example)
    // No Modifier = ᚨ
    // Shift + A = ᚩ
    // RAlt + A = ᚬ
    // Shift + RAlt = ᚭ

    name[Group1] = "Runic";

    key <AD01> { [ U16A6 ] }; // Q: ᚦ
    key <AD02> { [ U16B9 ] }; // W: ᚹ
    key <AD03> { [ U16D6 ] }; // E: ᛖ
    key <AD04> { [ U16B1 ] }; // R: ᚱ
    key <AD05> { // T: ᛏ/ᛐ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16CF, NoSymbol, NoSymbol, U16D0 ]
    };
    key <AD06> { [ U16C7 ] }; // Y: ᛇ
    key <AD07> { // U: ᚢ/ᚣ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16A2, U16A3, NoSymbol, NoSymbol ]
    };
    key <AD08> { [ U16C1 ] }; // I: ᛁ
    key <AD09> { [ U16DF ] }; // O: ᛟ
    key <AD10> { [ U16C8 ] }; // P: ᛈ

    key <AC01> { // A: ᚨ/ᚩ/ᚬ/ᚭ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16A8, U16A9, U16AC, U16AD ]
    };
    key <AC02> { // S: ᛊ/ᛋ/ᛌ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16CA, U16CB, NoSymbol, U16CC ]
    };
    key <AC03> { [ U16DE ] }; // D: ᛞ
    key <AC04> { [ U16A0 ] }; // F: ᚠ
    key <AC05> { [ U16B7 ] }; // G: ᚷ
    key <AC06> { // H: ᚺ/ᚻ/ᚼ/ᚽ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16BA, U16BB, U16BC, U16BD ]
    };
    key <AC07> { // J: ᛃ/ᛄ/ᛅ/ᛆ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16C3, U16C4, U16C5, U16C6 ]
    };
    key <AC08> { // K: ᚴ/ᚵ/ᚶ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16B2, U16B3, U16B4, NoSymbol ]
    };
    key <AC09> { [ U16DA ] }; // L: ᛚ

    key <AB01> { // Z: ᛉ/ᛦ/ᛧ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16C9, NoSymbol, U16E6, U16E7 ]
    };
    key <AB02> { // X: ᛜ/ᛝ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16DC, U16DD, NoSymbol, NoSymbol ]
    };
    key <AB03> { // C: ᚪ/ᚫ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16AA, U16AB, NoSymbol, NoSymbol ]
    };
    key <AB04> { // V: ᛠ/ᛡ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16E0, U16E1, NoSymbol, NoSymbol ]
    };
    key <AB05> { // B: ᛒ/ᛓ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16D2, NoSymbol, NoSymbol, U16D3 ]
    };
    key <AB06> { // N: ᚾ/ᚿ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16BE, NoSymbol, NoSymbol, U16BF ]
    };
    key <AB07> { // M: ᛘ/ᛙ/ᛚ
        type = "FOUR_LEVEL",
        symbols[Group1] = [ U16D7, NoSymbol, U16D8, U16D9 ]
    };

    // Punctuation keys with fourth-layer runes
    key <AC10> { // ;/:/᛭
        type = "FOUR_LEVEL",
        symbols[Group1] = [ semicolon, colon, U16ED, NoSymbol ]
    };
    key <AB08> { // ,/</᛫
        type = "FOUR_LEVEL",
        symbols[Group1] = [ comma, less, U16EB, NoSymbol ]
    };
    key <AB09> { // ./>/᛬
        type = "FOUR_LEVEL",
        symbols[Group1] = [ period, greater, U16EC, NoSymbol ]
    };

};

Install instructions:

1. The above layout file goes in /usr/share/X11/xkb/symbols/

• It's a write protected folder by default so cd there in your terminal and create a new file with sudo and call it runic

2. Now we have to update the Layout list at /usr/share/X11/xkb/rules/evdev.xml

• Open the file with sudo and follow the instructions carefully.
• Find the <layoutList> section of the file and go down to the last entry in the nest. It should be the user-defined custom layout section. We will create a new one for ours right above so we are the second-to-last in the list. It should look like so.
  

Pasting the entry here so you'll have an easier time copying it.

    <layout>
      <configItem>
        <name>runic</name>
        <shortDescription>Runic</shortDescription>
        <description>Custom Runic Keyboard Layout</description>
        <languageList>
          <iso639Id>run</iso639Id>
        </languageList>
      </configItem>
      <variantList/>
    </layout>

Once that's done you should be good to go!

Here's a preview of the layout:

Be sure to restart your system once and on KDE Plasma you can go to Keyboard > Layouts to add the new layout

Updated it! (1.0 -> 1.1)

• Moved Ȳr to the shift state of Ūruz
• Moved Ēar so it's the base state corresponding to Īor
• Gave Æsc its own binding as the shift state of Āc
• Made it more readable so you'll have an easier time modifying it

Preview:

Updated it! (1.1 -> 1.2)

We are now feature complete!

• RAlt layer now has runic single, double and cross punctuations.
• New shift state
  • Shift+RAlt now hosts short-twig forms of Younger Futhark where applicable.

Preview: