turning a keycode into a string?

Each Enum has a 'Value' key containing an ASCII code, so you could do

print(Enum.KeyCode.A.Value) -- 97

-- Convert ASCII value to a character
print(string.char(Enum.KeyCode.A.Value)) -- a

-- Get the uppercase ASCII value of the key code
print(string.char(Enum.KeyCode.A.Value):upper()) -- A

-- Get the ASCII value of the uppercase key code
print(string.byte(string.char(Enum.KeyCode.A.Value):upper())) -- 65

So for your case you could do

local player = game.Players.LocalPlayer
local userinputservice = game:GetService("UserInputService")
local bool = false -- going to make this turn on and off when a player enters a chair

userinputservice.InputBegan:Connect(function(object)
    print(string.char(object.KeyCode.Value):upper())
    if workspace.Seat:FindFirstChild("SeatWeld") then
        -- game.ReplicatedStorage.KeyBoard:InvokeServer(object.KeyCode)
    end 
end)

Take a look at this page for the keycodes:

https://developer.roblox.com/api-reference/enum/KeyCode

You probably won't need them, but its a good reference to have.

Since you can't get the specific KeyCode input by itself printed, you'd have to use the string library provided by Roblox to manipulate for your desired input.

This can be done in two steps: Converting the inputObject you receive from UserInputService.InputBegan into a string, then using substring to cut out unnecessary parts of the inputObject string.

function onKeyPress(inputObject, gameProcessedEvent)
    -- Converts the input into a string
        local keys = tostring(inputObject.KeyCode)

    --[[ Uses the substring function to get all characters after position 13
        Enum.KeyCode.E
                     ^ Position 14]]
        local result = string.sub(keys, 14, string.len(keys))

    -- Prints the end result
        print (result)
    end
game:GetService("UserInputService").InputBegan:connect(onKeyPress)

If there are any other questions feel free to contact me. Hope this helps!