Put these lines in your ~/.Xresources file to make xterm look like a VT240.

put_in_xresources.txt

// I'm a fan of old-school VT220 & VT340 terminals.  A
// while back I noticed Viacheslav Slavinsky created a
// TrueType typeface you could use with x/windows to
// make xterm look like a VT-whatever. You can download
// the original typeface from:
//
//   https://github.com/svofski/glasstty
//
// And there's a web page describing its creation at:
//
//   https://web.archive.org/web/20100219043225/http://sensi.org/~svo/glasstty/
//
// There's a modified version with a "straight" single
// tick-mark available at:
//
//   https://github.com/lalo/VT220-mod-font
//
// The original page by Slavinsky says they release the
// typeface into the public domain.
//
// In theory, you're supposed to copy the TTF font to
// the ~/.fonts/ or /usr/share/fonts/truetype/
// directories and run this command:
//
//   fc-cache -fv
//
// But on Ubuntu, I just double-clicked the TTF file to
// launch the font installer.  After clicking "Install"
// it put it in the ~/.local/share/fonts/ directory and
// it worked fine.
//
// Now add these lines to your ~/.Xresources file and
// log out and log back in, or run this command:
//
//   xrdb -merge < ~/.Xresources

XTerm*faceName: VT220\\-mod 
XTerm*faceSize: 15
XTerm*Background: #000000
XTerm*Foreground: #FF872F
XTerm*borderColor: #1A0E05
XTerm*decTerminalID: vt340
XTerm*numColorRegisters: 256
XTerm*scaleHeight: 1.0
XTerm*cursorBlink: false
XTerm*vt100.selectToClipboard: true
XTerm*vt100.internalBorder: 4
XTerm*vt100.colorInnerBorder: true
XTerm*vt100.forcePackedFont: true