very wip, but you should be able to use this w/ ESM version of noVNC which `rfb` is not available on browser console. YOU NEED TO SET REMOTE MACHINE'S KEYBOARD LAYOUT TO US ONE

wip.js

(async () => {
    async function inputToCanvas(input) {
        const needShift = '!"#$%&()}*+:>?@^_{|}~'
        const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms))
        const canvas = document.querySelector("#screen canvas")
        for (const char of input) {
            console.log(char)
            if (char === "\n") {
                const keydown = new KeyboardEvent("keydown", {
                    code: "Enter",
                    key: "Enter",
                })
                canvas.dispatchEvent(keydown)
                await sleep(50)
                continue
            }
            if (needShift.includes(char)) {
                const keydown = new KeyboardEvent("keydown", {
                    code: "ShiftLeft",
                    key: "Shift",
                    shiftKey: true,
                })
                canvas.dispatchEvent(keydown)
                await sleep(25)
            }
            const keydown = new KeyboardEvent("keydown", {
                code: "Unidentified",
                key: char,
                shiftKey: true,
            })
            canvas.dispatchEvent(keydown)
            await sleep(50)
            if (needShift.includes(char)) {
                const keydown = new KeyboardEvent("keyup", {
                    code: "ShiftLeft",
                    key: "Shift",
                    shiftKey: false,
                })
                canvas.dispatchEvent(keydown)
                await sleep(25)
            }
        }
    }

    inputToCanvas("echo Hello\n")
})()